Electrode mounting structure for providing insulation

ABSTRACT

An indicator discharge tube having an insulating mask in which a plurality of slits are formed with similar pattern to that of cathode electrodes disposed on an insulating baseplate, said insulating mask being arranged between said insulating baseplate and an anode electrode with a narrow gap from said insulating plate.

United States Patent ELECTRODE MOUNTING STRUCTURE FOR PROVIDINGINSULATION 3 Claims, 5 Drawing Figs.

U.S. Cl 313/109.5, 313/268, 313/205 Int. Cl 1101] l/90, H01 j 19/44Field of Search 3 l 3/109.5, 268, 259

[56] References Cited UNITED STATES PATENTS 2,632,128 3/1953 Hancock313/l09.5 X 3,278,779 10/1966 Szegho 313/259 X 3,281,619 10/1966 Greene3l3/l09.5 X 3,346,759 10/1967 Hardwick 3 l 3/l09.5

Primary Examiner- Eli Lieberman Assistan! ExaminerWm. 1-1. PunterAttorney-Hill, Sherman, Meroni, Gross & Simpson ABSTRACT: An indicatordischarge tube having an insulating mask in which a plurality of slitsare formed with similar pattern to that of cathode electrodes disposedon an insulating baseplate, said insulating mask being arranged betweensaid insulating baseplate and an anode electrode with a narrow gap fromsaid insulating plate.

ELECTRODE MOUNTING STRUCTURE FOR PROVIDING INSULATION BACKGROUND OF THEINVENTION 1 Field of the Invention The present invention relates to anindicator discharge tube, and more particularly to an indicatordischarge tube to display numerals, characters or the like through theuse of a plurality of electrodes arranged with a predetermined spacedrelation with each other.

2. Description of the Prior Art In the prior art indicator dischargetubes, drawbacks have arisen that the metal making up the cathodeelectrodes is sputtered therefrom when the discharge tube is appliedwith discharge voltage and finally the sputtered cathode metal particlescovers substantially the entire surface of the surface of an insulatingbaseplate between the adjacent cathode electrodes, which leads to shortcircuiting of the adjacent cathode electrodes to render theminoperative.

SUMMARY OF THE INVENTION Accordingly, the primary object of the presentinvention is to provide a novel indicator discharge tube which avoidsthe drawbacks such as short circuiting phenomena between the adjacentcathode electrodes caused by the so-called cathode sputtering."

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of aconventional prior art indicator discharge tube;

FIG. 2 is an enlarged cross-sectional view of a prior art device takenalong the line I-I in FIG. 1;

FIG. 3 is an enlarged cross-sectional view showing one example of thisinvention;

FIG. 4A is a front view illustrating an insulating baseplate used in theexample depicted in FIG. 3; and

FIG. 4B is a front view illustrating an insulating mask employed in theexample depicted in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Prior to a detailed descriptionof the present invention, one example of conventional prior artindicator discharge tubes wiil be described in detail with reference toFIGS. 1 and 2.

A conventional indicator discharge tube is shown in FIGS. 1 and 2. InFIG. I, reference numeral 1 designates an airtight envelope made of atransparent glass and 2 a stem made of ceramic. Reference numeral 3represents an insulating baseplate which has formed therein a pluralityof grooves 4 arranged in a predetermined pattern, the predeterminedpattern being number 8 in this example. Cathode electrodes 5 made of,for example, nickel, tantalum, stainless steel or the like are embeddedin the grooves 4 respectively. In this case the cathode electrodes areembedded in a manner not to jut beyond the surface 3' of the baseplate3. A gridlike or meshlike anode electrode 6 is disposed in opposing butspaced relation to the insulating baseplate 3. The gridlike or meshlikeanode electrode 6 is fixedly supported at both side edges thereof withsupport frames 7 and at front and back surfaces thereof with shockproofmica plates 8 to thereby keep the relationship between the anodeelectrode 6 and the cathode electrodes 5. Lead wires 9 connected at oneend thereof to the respective cathode electrodes 5 and the anodeelectrode 6 are led out to the back surface of the insulating baseplate3 through apertures (not shown) bored therethrough and further led tothe outside of the airtight envelope 1 through the stem 2 used to heleads for connecting the other ends to other electric circuit elements.The airtight envelope 1 is filled with an inert gas such as neon, argonor the like or a mixture of them at a pressure in the range of aboutseveral tens to 100 mm. of Hg. With such an arrangement, when the tubeis subjected to discharge, the metal making up the cathode electrodes 5is disposed on the surface portion 3 of the insulating baseplate 3between and in the vicinity of the adjacent cathode electrodes 5 due tothe sputtering as metal particles indicated at dots 10 in FIG. 2 andfinally all the surface 3'. This sputtering phenomena cause in practicaluse such fatal defects as short circuiting of the adjacent cathodeelectrode 5 with the metal particles 10 on the surface 3' of theinsulating baseplate 3 to bring the tube to be of no use.

In view of the foregoing drawbacks of the prior art, this invention isto provide an indicator discharge tube in which an insulating mask asshow in FIG. 3 and 4B is inserted between an anode electrode and cathodeelectrodes.

With reference to FIGS. 3 and 4, a description will hereinafter be givenof one example of the present invention in detail.

In FIGS. 3 and 4 similar elements to those in FIGS. 1 and 2 areidentified by the similar reference numerals and are omitted thedescription thereof.

In this invention, an insulating mask 12 is disposed on the insulatingbaseplate 3 for respectively insulating the adjacent cathode electrodes5. In this case the insulating mask 12 is disposed in such a manner thata narrow gap 11 is formed between the insulating mask 12 and theinsulating baseplate 3. The anode electrode 6 is disposed in opposingbut spaced relation to both the cathode electrodes 5 and the insulatingmask 12.

Further, a description will hereinafter be given in detail on theexample.

A plurality of shallow grooves 13 are fonned in the front surface of theinsulating baseplate 3 enough to sufficiently hold the cathodeelectrodes 5 thereon. The insulating mask 12 is disposed on theinsulating baseplate 3 through thin insulating spacers 14 made of micaor like material therebetween to respectively insulate the adjacentcathode electrodes 5. A plurality of slits or slots 15 are formed in theinsulating mask 12 at places corresponding to the cathode electrodes 5so that the cathode electrodes 5 can be seen through the slits 15 of theinsulating mask 12. The anode electrode 6 is disposed in opposing andspaced relation to the insulating mask 12 at the outer side opposing tothe baseplate 3 with respect to the insulating mask 12. The anodeelectrode 6 is gridlike or meshlike similar to that in FIG. 1 example.Lead wires (pot shown) for the cathode electrode and the anode electrodeare respectively led out to the back of the insulating baseplate 3 fromthe cathode electrodes 5 and the anode electrode 6 through bores (notshown) formed in the insulating baseplate 3 and also through the stem 2as in FIG. 1 example.

With such a construction, a discharge voltage is supplied across thecathode electrodes 5 and the anode electrode 6 to produce glowdischarge. Due to the glow discharge, the metal making up the cathodeelectrodes is sputtered therefrom to the portions in the vicinity of thecathode electrodes 5, that is, the sputtered metal particles aredeposited on the surface of the insulating baseplate 3 and theinsulating mask 12 in the vicinity of the cathode electrodes 5 asindicated by dots 10, which is similar to that in FIG. 1 example.However, since in the present invention the narrow gap 11 having adistance 3 is formed between the insulating mask 12 and the distance gis selected narrow, for example, as 0.05 mm. to 0.l mm., the cathodemetal particles do not sputter into the gap II remote from the openingthereof. That is, the sputtered cathode metal particles are notdeposited on the entire surfaces of the insulating mask 12 andinsulating baseplate 3 between the adjacent cathode electrodes.Consequently, the indicator discharge tubes according to the presentinvention has a longlife insulation between the cathode electrodes 5.

According to the present invention such an advantage as the trouble ofthe short circuiting between the cathode electrodes is prevented isattained.

It will be apparent that many modifications and variations may beeffected without departing from the scope of the novel concepts of thisinvention.

We claim as our invention:

mask being disposed in such a manner to provide a narrow gap between theinsulating baseplate and the insulating mask.

2. An indicator discharge tube as claimed in claim 1, wherein a spaceris inserted between the insulating baseplate and the insulating mask.

3. An indicator discharge tube as claimed in claim 1, wherein thedistance of the gap is selected to be the range of 0.05 mm. to 0.1 mm.

* I t l

1. An indicator discharge tube comprising an insulating baseplate havinga plurality of grooves formed thereon in a predetermined pattern, aplurality of cathode electrodes disposed in the grooves of theinsulating baseplate respectively, a single anode electrode disposedcommon to the plurality of cathode electrodes with a space, and aninsulating mask insulating the plurality of cathode electrodesrespectively having a plurality of slits substantially in similarpatterns to that of the grooves formed in the insulating baseplate, theinsulating mask being disposed in such a manner to provide a narrow gapbetween the insulating baseplate and the insulating mask.
 2. Anindicator discharge tube as claimed in claim 1, wherein a spacer isinserted between the insulating baseplate and the insulating mask.
 3. Anindicator discharge tube as claimed in claim 1, wherein the distance ofthe gap is selected to be the range of 0.05 mm. to 0.1 mm.